This invention relates to storage systems, and, more particularly, to a controlled atmosphere storage facility for storing containers of products such as agricultural produce.
Most agricultural products are produced in a seasonal fashion. That is, the crops do not mature uniformly throughout the year. There is usually a peak production season when a large volume of the product is harvested and available, and then a long off-season when the product is not readily available from the producers.
The crop cycle is significant for agricultural producers, processors, and consumers. The prices paid for crops are usually lowest during the harvest period, resulting in low prices to the farmers. Processors of products are overloaded for a brief period, and then idle during the off-season. Consumers have fresh product available for only a limited period.
Preservation techniques such as canning, drying, and freezing make the produce available in those forms for longer periods. However, each of these procedures changes the essential nature of the food product. Thus, for example, a canned, dried, or frozen apple is simply not the same as a fresh apple.
When fresh food products such as apples or pears are stored in air for an extended period of time, they dehydrate and alter chemically, becoming less acceptable for processing and to consumers. Storage procedures have been developed for storing such fruits in a controlled atmosphere of, for example, 2 percent oxygen, 2 percent carbon dioxide, balance nitrogen. When stored in such an atmosphere for extended periods of time, such as 3-12 months, the fruit retains its essential quality at harvest. By this approach, consumers can have available certain types of fresh fruit throughout the year.
Controlled atmosphere storage facilities, in some cases refrigerated to about freezing temperature, have been increasingly used to store apples in such states as Washington and California. Such a facility typically includes a large enclosure made of sheet metal having joints that are sealed as tightly as possible. Containers of the produce are loaded into the enclosure, and the door sealed. The controlled atmosphere is introduced, and the interior cooled.
While operable for its purpose, such a storage facility has several important practical disadvantages. It may take at least a week to establish the controlled atmosphere and cool the product to the storage temperature. During that week, the quality of the fruit degrades. Also, it is necessary to accumulate an amount of fruit sufficient to fill the storage facility before it is sealed, again causing a delay in the product reaching the storage condition. Although controlled atmosphere certification regulations may permit such delays, they are nevertheless undesirable. When the produce is to be removed from the facility, the door seal is broken, and the entire contents of the facility subjected to atmospheric conditions so that the product can be removed. There is then a brief oversupply of the product, and thereafter, once again, none is readily available. The product to be stored must be homogeneous in the sense that all of it is loaded into the storage facility at once, and is removed at once. The existing storage facilities are not suited to storing a diversity of products at the same time. Finally, the conventional construction of the storage facility is uneconomical if the size is relatively small, and results in heat and gas leaks if the facility is relatively large.
One approach to an improved storage approach has been to place the articles to be stored into individually sealed containers. The protective atmosphere is established within the container, which may also be placed into a cooled storage locker. While perhaps acceptable for small items and small quantities, such an approach is not practical for the storage of large amounts of large containers.
There is therefore a need for an improved storage facility for agricultural produce and other articles that require protected storage. The present invention fulfills this need, and further provides related advantages.